Increasing research activities have been under way recently to develop illumination devices in which an excitation light source generates excitation light which is then projected to a light emitting section containing a fluorescent material so that the material can emit illumination light. The excitation light source here is a semiconductor-based light emitting element, such as an LED (light emitting diode) or an LD (laser diode).
For example, Patent Literatures 1 and 2 disclose technology related to such illumination devices.
Patent Literature 1 discloses a lamp device which includes a first optical member (lens), a second optical member (reflector), and a fluorescent material. In the lamp device, the first optical member converges excitation light from a light source (laser diode) which is then projected to a fluorescent material, so as to emit high luminance light from a small region. This mechanism ensures brightness of a hotspot (a part, of an alignment region, which needs to be illustrated brightly). Patent Literature 1 also describes an example where the lamp device is arranged to guide the excitation light to the first optical member through an optical fiber.
Patent Literature 2 discloses a light source device including: a laser diode which emits short-wavelength laser light; a collimator lens which collimates the laser light from the laser diode so as to form parallel fluxes of light; a condenser which converges the laser light, now in the form of parallel fluxes of light, from the collimator lens; and a fluorescent material which absorbs the laser light converged by the condenser and spontaneously emits incoherent light.